Synthesis, characterization, and application of functional nanomaterials

The controlled design and synthesis of functional nanomaterials is of great interest for both fundamental and applied science. This thesis is primarily focused on the synthesis of unique transition metal nanoparticles with a focus on their fundamental optical, morphological, and electronic conductivity properties.;To this end, extensive research has been focused on the development of gold and silver nanoparticles which are passivated primarily by alkanethiol molecules where the bonding to the metal core and the organic molecule is via the sulfur atom. Such "monolayer protected clusters" (MPCs) have been thoroughly characterized optically, electrochemically, and morphologically. However, studies on more exotic metals have to this point been limited. One of the limiting factors has been the difficulty in producing stable MPCs of these desired metals. This lack of stability often stems from the relatively weak bonding strength between sulfur and many of these metals. To circumvent this issue and synthesis a wider range of stable, tunable metal nanoparticles, metal-carbon bonding was explored. In many cases, the metal-carbon bond is much stronger than the metal-sulfur bond, a fact which leads to more long-term stability of many metal nanoparticles.;In this study, palladium, titanium, ruthenium, and iridium nanoparticles were designed using metal-carbon bonding by utilizing a phenyl diazonium derivatives where the organic ligand bonded to the metal core through a carbon radical on the phenyl portion of the diazonium molecule. Not only did this metal-carbon bonding lead to stable and tunable nanoparticles, the metal-carbon bonding also lead to very interesting features in the electronic conductivity of these nanoparticles.;In the case of the palladium nanoparticles, the conduction properties for a set of Pd particles passivated by a biphenyl molecule exhibited metallic conduction behavior over a range of 80--300K. By introducing alkyl spacers, Pd-decylphenyl particles passivated showed a Mott-Hubbard transition at roughly 180K. Such interesting features in the electronic conductivity of palladium nanoparticles lead to the synthesis of six different types of ruthenium nanoparticles where the passivating ligand was altered by two alkyl spacers ranging from butyl- to dodecylphenyl. From these set of six particles, the electronic coupling coefficient beta was determined to be 0.48 A-1 leading to far enhanced conduction as compared to beta values for metal-sulfur bonded nanoparticles.;The strong bond strength of the metal-carbon bond lead to the novel synthesis of titanium nanoparticles. Synthesis of metallic titanium is quite difficult due to the rapid oxidation of titanium and the formation of titania rather than titanium. However, with the use of the metal-carbon bonding facilitated synthesis, titanium nanoparticles were synthesized using simple solution chemistry. To ensure that the as-synthesized particles were indeed titanium and not the titanium oxides, HRTEM, Uv-Vis, and solid-state conductivity measurements were carried out to compare both species.;Applications of nanomaterials is the ultimate goal in their design and synthesis. Iridium nanoparticles were synthesized using the metal-carbon bonding recipe and utilized in two applications. First, these iridium nanoparticles were used to detect trace levels of mercury and using these newly formed mercury electrodes, trace levels of heavy metal ions were also detectable. Also, these as-prepared iridium nanoparticles were used to form IrO2 nanoparticle and were examined along with NiO nanoparticles for their electrochromic properties. In previous studies of electrochromism of these materials, nanoparticles were not used, but bulk or thin films were studied. This was the first use of IrO 2 and NiO nanoparticles in this application.